EIGER III. JWST/NIRCam observations of the ultra-luminous high-redshift quasar J0100+2802

TL;DR

This study presents JWST/NIRCam observations of the most luminous high-redshift quasar, measuring its supermassive black hole mass, analyzing gravitational lensing effects, and confirming its intrinsic luminosity and black hole size less than 1 billion years after the Big Bang.

Contribution

First rest-frame optical spectrum of a high-redshift quasar with JWST/NIRCam, providing accurate SMBH mass measurement and lensing analysis to confirm its intrinsic luminosity.

Findings

SMBH mass estimated at ~10^10 solar masses

No evidence of strong gravitational lensing

Quasar's black hole formed within 1 Gyr after Big Bang

Abstract

We present the first rest-frame optical spectrum of a high-redshift quasar observed with JWST/NIRCam in Wide Field Slitless (WFSS) mode. The observed quasar, J0100+2802, is the most luminous quasar known at $z>6$. We measure the mass of the central supermassive black hole (SMBH) by means of the rest-frame optical H$\beta$ emission line, and find consistent mass measurements of the quasar's SMBH of $M_\bullet\approx10^{10}\,M_\odot$ when compared to the estimates based on the properties of rest-frame UV emission lines CIV and MgII, which are accessible from ground-based observatories. To this end, we also present a newly reduced rest-frame UV spectrum of the quasar observed with X-Shooter/VLT and FIRE/Magellan for a total of 16.8 hours. We readdress the question whether this ultra-luminous quasar could be effected by strong gravitational lensing making use of the diffraction limited NIRCam images in three different wide band filters (F115W, F200W, F356W), which improves the achieved spatial resolution compared to previous images taken with the Hubble Space Telescope by a factor of two. We do not find any evidence for a foreground deflecting galaxy, nor for multiple images of the quasar, and determine the probability for magnification due to strong gravitational lensing with image separations below the diffraction limit of $\Delta\theta\lesssim 0.05''$ to be $\lesssim 2.2\times 10^{-3}$. Our observations therefore confirm that this quasar hosts a ten billion solar mass black hole less than $1$ Gyr after the Big Bang, which is challenging to explain with current black hole formation models.